Conventionally, regarding switches for opening and closing contacts according to the movement of a plunger, switches that are provided with a coil spring for returning the plunger are known. For example, JP 2013-541145A discloses an emergency stop switch that is provided with a coil spring on a lower side in a direction in which the plunger moves.
JP 2013-541145A (published on Nov. 7, 2013) is an example of background art.